This invention relates to fastener and more particularly to thread locking type blind hollow fasteners that can be installed entirely from one side of an apertured workpiece wherein the body portion of the hollow fastener has an intermediate portion that is tapered to control the upsetting or bulging of such intermediate portion of the fastener for use on a range of sizes or thicknesses of apertured workpieces. Such blind fasteners are used where it is not practical or possible to drill and tap the structure or where the other side of the structure is non-accessible.
Various designs of blind fasteners consisting of threaded tubular bodies which can be inserted through a hole in a structure and expanded to bear against the back or blind side of the structure have a threaded portion which will function as a stationary nut for fastening the desired external component. The upsetting process which expands that portion of the fastener against the back surface of the structure must be secure enough and complete to secure such fastener firmly. To prevent problems of rotation of the fastener where torquing of the screw is made it is important to assure the collapsing of that portion of the fastener against the bottom of the apertured workpiece by selecting the proper size and length of fastener body. The present invention contemplates the configuration of the intermediate hollow body portion of the fastener into a taper with the thinner portion thereof more closely to the head portion of the body portion to control the upsetting action of the fastener. If the workpiece is thicker the installation hole or apertured workpiece reinforces the thin intermediate portion of the taper and upset occurs at the thick portion of the taper. If the workpiece is thin, then the thin portion of the taper upsets first thus providing a single fastener that can accommodate variations in thickness of the workpiece. Such fasteners have particular advantage in composite materials where thickness typically varies greatly.